Board Thread:Classic DMC/@comment-36444075-20190321220539/@comment-28055547-20190322124015

DT + Air Hike + Helm Breaker on his back with Alastor deals a TON of damage, if you hit the sweet spot. Even if you don't, still nice damage and likely to stagger him. Outside of DT, keep to his side and hit him - while it won't damage him, it will still give you DT. Unfortunately, Air Raid doesn't work as well as it did on Normal/Hard.

Alternatively, Nightmare-Beta ignores Phantom's armor and will hit him hard. But, you have to stay still to use it, and need DT. One advice - if you're already in DT when you start charging Nightmare, it won't cost more (unconfirmed)